
(define (A x y)
  (cond ((= y 0) 0)
        ((= x 0) (* 2 y))
        ((= y 1) 2)
        (else (A (- x 1)
                 (A x (- y 1))))))

(A 1 10) ;1024
(A 2 4)  ;65536
(A 3 3)  ;65536

(define (f n) (A 0 n)) ;2y
(define (g n) (A 1 n)) ;2^n
(define (h n) (A 2 n)) ;2^(2^(2^(....^(2^2)))) (共n个2） 
(define (k n) (* 5 n n)) ;5*n^2

(g 5)

(h 3)
